How to do a root cause analysis that finds the real cause
In short: How to do a root cause analysis: deal with the immediate problem first, then gather the facts and keep asking why until you reach something in the way the work is set up that you can change. Fix the process, not the person, and check a few weeks later that it has stopped. Done properly, you stop paying for the same mistake twice. Use our free root cause analysis worksheet to find the real cause of your next problem.
A root cause analysis is a step-by-step way of finding the real reason a problem happened, so you can fix the cause rather than just the symptom.
Written by Mike Armstrong. Last reviewed: 22 October 2026.
When late visits started creeping up at my care company, the first thing we did was talk to the carer involved, and that was the right place to start. The mistake would have been to stop there. The carers weren’t the problem; the way we planned their day was, and it was costing us money every week we didn’t see it. That lesson has stayed with me ever since: the person standing next to a problem is rarely the cause of it.
Now picture a different business. It’s Tuesday afternoon, and a customer is on the phone. Their order has gone to their old address. Again. Someone apologises, someone sends a replacement by express post, and someone, usually the manager, has a quiet word with whoever packed it. Problem solved.
Three weeks later, it happens again.
Dave saw it coming.
Let me introduce you to Dave. Dave’s been here for years, knows absolutely everything and could pack an order in his sleep. He’s friendly, very practical and never has a bad word to say about the place. He could tell you exactly why the parcels keep going astray: the labels are printed first thing in the morning, before anyone has read the emails from customers who’ve moved house. Nobody has asked him.
In this guide, you’ll learn why the same problems keep coming back, the difference between fixing today’s problem and fixing its cause, an eight-step method for finding the real cause, and how to check your fix has worked. There are two real examples from businesses I’ve run, and one famous example that turned out to be more complicated than anyone admits. And stick around to the end, because Dave gets the last word.
Free root cause analysis worksheet inside, no sign-up needed. Get it here.
Why the same problems keep coming back
When something goes wrong, the natural reaction is to fix what’s in front of you: refund the customer, redo the job, have a word. That deals with today. It does nothing about next month, because whatever caused the problem is still sitting there, waiting for the next busy Tuesday.
The Health and Safety Executive, the UK’s workplace safety regulator, puts it bluntly in its guide to investigating incidents, HSG245: “Blaming individuals is ultimately fruitless.” It adds that investigations which conclude operator error was the sole cause “are rarely acceptable”. HSE is writing about safety, but the same logic tends to hold for a late delivery or a wrong invoice.
The cost adds up quietly. The same HSE guide notes that a business’s uninsured costs can be 8 to 36 times what it spends on insurance. Repeat mistakes tend to work the same way: the refund is the cost you see. The lost time, the rework and the customer who quietly stops ordering are the costs you don’t.
To fix the cause, you first need to be clear about what a cause is, because three terms get muddled all the time.
Immediate action, root cause and corrective action: what’s the difference?
Here’s the plain version, using the wrong-address parcels from the start of this guide.
| Immediate action | Root cause | Corrective action | |
|---|---|---|---|
| What it is | What you do straight away to protect the customer | The real reason the problem happened, in the way the work is set up | The change you make to remove the root cause |
| When | The same day | Found by investigating, often over days or weeks | Once you know the root cause |
| Example | Send a new parcel by express post | The dispatch procedure has no step to check for address changes before labels are printed | Add that step to the procedure and brief the packing team |
| What it fixes | Today’s problem | Nothing on its own; it tells you what to fix | Makes the problem far less likely to happen again |
HSE draws the same line. It describes the immediate cause as “the most obvious reason why an adverse event happens”, and the root cause as “an initiating event or failing from which all other causes or failings spring”. You need both. The immediate action protects the customer today; the corrective action protects every customer after them. If the problem began as an accident or a near miss at work, our Learn page on how to write an incident report shows you how to record the facts first.
So that’s what you’re looking for. Now here’s how to find it.
The method: how to do a root cause analysis in eight steps
The first two steps get the problem under control, the next three find the cause, and the last three fix it and make sure it stays fixed.
1. Make it safe to tell the truth
Before you ask anyone a single question, say clearly that this isn’t a witch hunt and nobody is going to get into trouble. Get the owner to say it too, in front of the team. A full and accurate account of what happened is the most useful thing anyone can give you, and people only tend to give one when they’re not worried about the reaction.
Then give them a reason to want to help. Something like: “We’re looking for what in the way we work let this happen. If we work it out together, we can fix it, the job gets easier for all of us, and we’ll spend less time putting things right and more time enjoying the work.” People who feel part of the fix tend to tell you far more than people who feel investigated.
2. Deal with the immediate problem
Protect the customer first. Replace the item, hold back the rest of the stock, check the rest of the batch, and tell the customer what you’re doing about it. Write down what you did and when. This is the immediate action, and it buys you the time to find the cause properly instead of in a panic. Dave, meanwhile, has already found a replacement and the express post form, because he knew you’d ask.
3. Gather the facts
Talk to the person who was there. That’s the right place to start, as long as you don’t stop there. Then look at the evidence: the records, the emails, photos, any video or CCTV footage, and the procedure for the job, if there is one. Include at least one person who does the job every day, because they often know the cause before anyone else does. Ask Dave. Put the kettle on first; he’s been waiting a while.
Write down facts, not opinions. “The label was printed at 8.15am and the customer’s email arrived at 8.40am” is a fact. “Sam wasn’t concentrating” is an opinion, and probably an unfair one.
4. Ask why until you reach the process
Start with the problem and ask why it happened. Then ask why that happened, and keep going until you reach something in the way the work is set up that you can change. This is a problem-solving technique called the five whys, and it comes from Toyota. Taiichi Ohno, the engineer behind the Toyota Production System, described repeating “why” five times as the basis of Toyota’s scientific approach, in his book Toyota Production System (1988).
Here’s how it looks with the wrong-address parcels:
- Why did the parcel go to the old address? Because the label had the old address on it.
- Why did the label have the old address? Because it was printed before that morning’s address-change emails had been read.
- Why were they printed first? Because those emails go to the general inbox, which isn’t checked before labels are printed.
- Why isn’t it checked? Because the dispatch procedure has no step to check for address changes before printing.
Four whys, not five, and that’s fine. Five is a guide, not a rule: stop when you reach a cause you can fix, and back every answer with evidence. Dave could have told you the answer at the first why, of course, but he likes to see people get there on their own.
The famous example that turned out to be more complicated
If you research the five whys, you’ll likely come across the Jefferson Memorial in Washington DC. The popular version goes like this. The stone was wearing away. Why? It was cleaned too often. Why? Because of bird droppings. Why so many birds? They came to eat the spiders. Why so many spiders? They came to eat the midges. Why so many midges? They were drawn in by the floodlights at dusk. The fix: switch the lights on an hour later. Simple.
Except it wasn’t. Sologic, a firm of root cause analysis specialists, went back to the public records and found a messier story. Several Washington memorials had the same problem, not just the Jefferson. The real study was a year-long project by a team of specialists. The midges themselves did much of the staining, and the volume and pressure of the cleaning water played a big part. The lighting change cut the insects by about 85% within weeks, but it was only a six-week trial, and it was dropped after complaints from residents, businesses and photographers. Everyone loved the answer except the people who had to live with it.
The lesson isn’t that the five whys doesn’t work. It’s that real problems usually have more than one cause, and a neat chain of whys can miss some of them. That’s exactly why the next step exists.
5. Check the usual suspects
To make sure nothing’s been missed, run through six areas where causes tend to hide. They come from the fishbone diagram, developed by the Japanese quality expert Kaoru Ishikawa, but you don’t need to draw a fish; a simple checklist does the same job.
- People: training, experience, workload. Did they know how to do it, and did they have time?
- Method: the procedure or the way the job is done. Is there one, and is it right?
- Materials: supplies, parts and information coming in. Was something wrong before it reached you?
- Equipment: tools, machines and software. Did anything fail, or make the mistake easy?
- Surroundings: the workspace, time pressure, interruptions. Was it the busiest Tuesday of the year? Dave will tell you they all are.
- Measurement: checks, gauges, how you know it’s right. Would anyone have spotted it?
Note anything that played a part. With the root cause and any contributing causes on paper, you’re ready to fix them.
6. Fix the process
Decide what you’ll change so the problem is far less likely to happen again. Often it’s a missing or unclear step in a procedure, a gap in someone’s training, or a check that nobody actually does. Give every action one owner and a due date. An action without an owner tends to become a good intention, and good intentions don’t fix parcels.
If you’d rather not start from a blank page, our Root Cause Analysis Template takes you through every step, with a five whys table, the six-area check and a corrective action plan ready to fill in.
7. Check it worked
Don’t close it the day the fix goes in. Decide how and when you’ll check, then look again a few weeks later. If the problem has come back, reopen the investigation and look again at the cause. A problem that returns three months later was never solved; it was only patched.
8. Share what you learned
Tell the people who need to know, and update whatever the fix touched: the procedure, the training, your list of risks. Otherwise the fix lives in one person’s head, usually Dave’s, and walks out of the door when he retires.
Free printable root cause analysis worksheet
Those are the eight steps. The hardest part isn’t any one of them, though. It’s keeping your eye on the process when everyone’s instinct is to look at a person.
Process, not person (and when it really is a person)
The aim is not to find the person who got it wrong. It is to find the part of the process that let it go wrong. Fix the process, and whoever does the job next is far less likely to make the same mistake.
That doesn’t mean nobody is ever responsible. Once the process is sound, the odd person who still gets it wrong stands out clearly, and you can deal with it fairly as a performance issue, with the evidence in front of you. Fix the process first; it’s the only way to see the people clearly.
When the fix is a missing or unclear step, write it into a procedure. Our free guide to writing a standard operating procedure shows you how, and our SOP Template gives you the layout. When the cause is training, a skills matrix shows at a glance who can do what.
Does it work? Two root cause analysis examples from my own experience
That’s the method. Here’s what it looked like in two very different businesses I helped run.
Late visits at a care company
A couple of years into running my care company, we’d grown. Our carers made visits of half an hour to an hour to clients across a whole region, and as the number of visits went up, late arrivals started to creep up too. One or two complaints came in. At first it looked like a one-off, and we talked to the carer involved.
When the complaints kept coming, I spent a few weeks looking properly. I did a proper analysis of the visits and talked to all the carers. The cause wasn’t the carers at all. As we’d grown, carers were increasingly being sent from one end of the region to the other between visits. More time driving meant less time caring, and more late arrivals.
So we split the region into smaller areas and set our scheduling software to give each carer visits close to where they lived, grouped as much as possible in one area each day. A couple of months later, late visits had come right down. They still happened now and then, through traffic or an accident, but far less often.
The carers were happier because they spent less time driving. Our clients were happier because their carer turned up on time. And the business was better off, because we could only bill for care hours, never for driving time. Every minute saved on the road was a minute we could bill. One fix cut the complaints and raised our revenue, with the same team.
Reports that didn’t add up at a maritime security company
As Deputy Director of Operations at a maritime security company, I relied on the report our team leaders wrote after every transit. We weren’t on board the ship, so that report was our only real picture of what had happened, and we used it to report to our clients.
The reports were inconsistent. Some team leaders were excellent at them; others weren’t. It would have been easy to decide the problem was the people, because the team leaders came from different backgrounds, with very different experience of writing reports. But when I looked properly, the real cause was the procedure. It assumed every team leader already knew how to write a good post-transit report, and what it was for.
So I fixed the process, not the people. I created a structured report form with mandatory sections, and examples in each one of what belonged there. It worked almost like a checklist, and it prompted them to complete the corrective action reports and training records that had been missed before.
The effect was immediate. The reports came back consistent, and putting together the client report became easy. Now and again a poor report still came in, but now it stood out, and I could deal with that one person fairly.
Both fixes started the same way: a written investigation that went past the obvious answer. If you’d like a ready-made form for yours, the Root Cause Analysis Template has every step laid out, with a worked example to copy.
Where root cause analysis fits in ISO 9001
If you ever go for ISO 9001 certification, this is what the standard calls corrective action (clause 10.2). When something goes wrong, it expects you to react to it, find the cause, act on it, check that the action worked and update your system where needed. It doesn’t tell you which method to use, but a written root cause analysis is exactly the kind of evidence an assessor will want to see. If you’re wondering where preventive action fits in, our Learn page on the difference between corrective and preventive action explains it, with examples.
It matters commercially, too. There are more than a million ISO 9001 certificates across 189 countries, according to the ISO Survey, so the buyer usually has a certified competitor to turn to instead.
Our ISO 9001:2026 Certification-Ready System includes the full corrective action procedure, form and register, ready to adapt. And when you’re ready, we offer unaccredited remote certification.
Free download: the root cause analysis worksheet
To help you put this into practice, the eight steps, a five whys table and the six-area check all fit on one printable worksheet. No sign-up needed.
Get the free root cause analysis worksheet
Frequently asked questions
What are the steps of a root cause analysis?
Deal with the immediate problem, gather the facts, ask why until you reach the process, check the usual suspects, fix the process, check it worked and share what you learned. Before any of that, make it safe for people to tell you the truth, or the facts you gather won’t be the real ones.
What is a good root cause analysis example?
A good example ends at something in the way the work is set up, not at a person. In my care company, late visits were traced to carers being sent across a whole region; splitting it into smaller areas brought late visits right down and raised the hours we could bill.
What are the five whys?
The five whys is a technique from Toyota: you ask why a problem happened, then why that happened, and so on until you reach a cause you can fix. Five is a guide, not a rule, and it works best alongside a check of the other likely causes.
What is a fishbone diagram?
A fishbone diagram, developed by Kaoru Ishikawa, sorts the possible causes of a problem into groups such as people, method, materials, equipment, surroundings and measurement. You can use the same groups as a simple checklist instead of drawing the diagram.
Who should do a root cause analysis?
Ideally, someone who wasn’t directly involved leads it, with at least one person who does the job every day. In a small business that’s often the owner or a manager, working with the team rather than investigating them.
How long does a root cause analysis take?
A simple problem can be investigated in an hour or two. A problem that keeps coming back may take a few weeks of looking at records and talking to people, as it did with the late visits at my care company.
Does ISO 9001 require a root cause analysis?
ISO 9001 requires you to find the causes of a nonconformity, meaning anything that didn’t meet a requirement, and to act on them (clause 10.2). It doesn’t name a method; a written root cause analysis is a common, practical way to show you’ve done it.
The short version
If you remember nothing else from this guide, remember these five things.
- Deal with today first, then find the cause.
- Make it safe to tell the truth, or you’ll never hear it.
- Ask why until you reach the process, and check the other usual suspects.
- Fix the process, not the person, with an owner and a date for every action.
- Check it worked, and reopen it if it didn’t.
And Dave’s advice? “Before you have a word with me, have a look at how the job’s set up.”
What next?
If you’re investigating a problem right now, start with the free worksheet and work through the eight steps.
If you’d like a proper written record, our Root Cause Analysis Template gives you the full investigation and corrective action plan, with a worked example to copy. And if you’re building a whole management system, The ISO 9001:2026 Certification-Ready System has every procedure, form and register ready for you to adapt, with certification there if and when you want it.
About the author
Written by Mike Armstrong, senior ISO consultant, former company director, and founder of Plain Standards. In over 30 years running companies at director level, Mike built his own management systems to drive profit long before he adopted ISO 9001, so he comes at this from the owner’s side, not the auditor’s. Plain Standards helps small and medium sized businesses get ISO certified without a consultant.